During World War II metro stations were supposed to be used as a civil defense unit. In April 1941, Council of People's Commissars decreed that underground railway was to be accommodated to a mass bomb-proof shelter. After the war new metro stations in the USSR were being designed considering a probability the potential enemy might use weapons of mass destruction — atomic, chemical and bacteriologic. Airshafts were equipped with filters. So, in case of a zombie virus epidemic a metro station can be a long-term shelter for the survivors.